Preparation method of Bi-2212 precursor powder capable of remarkably improving phase density of Bi-2201 nanometer stripes in Bi-2212 wire

Abstract

The invention discloses a preparation method of Bi-2212 precursor powder capable of remarkably improving the phase density of Bi-2201 nanometer stripes in a Bi-2212 wire rod, and the Bi-2212 precursor powder capable of remarkably improving the phase density of the Bi-2201 nanometer stripes in the Bi-2212 wire rod is obtained by controlling the components of a precursor solution, adjusting in cooperation with a fine heat treatment method and controlling the molar ratio of Sr to Ca. According to the method disclosed by the invention, the components of the precursor solution are controlled, the large-size Bi-2201 phase is eliminated in combination with heat treatment, and the molar ratio of powder Sr to Ca is controlled to be within a proper range, so that the density of the nano stripe Bi-2201 phase in the Bi-2212 wire rod is improved, and the pinning performance of the Bi-2212 wire rod is favorably improved; the method is easy to operate, low in cost and high in controllability and operability, the cost performance of the Bi-2212 superconducting wire is improved, and rapid application of the Bi-2212 superconducting wire in the field of high-temperature superconducting magnets is further promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-temperature superconducting material preparation, and particularly relates to a preparation method of Bi-2212 precursor powder for significantly improving the density of Bi-2201 nano-stripe phases in Bi-2212 wires. BACKGROUND

[0002] Although the high-pressure heat treatment wire method reported internationally and the use of key technologies such as the preparation of Bi-2212 powder based on the spray chemical combustion method significantly improve the critical current density of Bi-2212 superconducting materials, the use of silver matrix in Bi-2212 superconducting materials still makes the cost high. Only by further improving the critical current density of Bi-2212 superconducting materials can the performance-price ratio of Bi-2212 superconducting materials be further improved, and the application process of Bi-2212 superconducting materials in future large high-field magnets can be finally promoted.

[0003] The application scenarios of Bi-2212 wires are mainly low-temperature high-field, and with the increase of field strength, the current-carrying performance of the wire decreases, which is a common natural phenomenon. At present, there are mainly two methods to improve the high-field current-carrying performance of Bi-2212 wires, one is to improve the intrinsic current-carrying performance of Bi-2212 wires under self-field, and the current-carrying performance under high field is also correspondingly higher; the other is to improve the pinning strength of Bi-2212 wires, and reduce the decay rate of current-carrying performance with magnetic field. The existing research has preliminarily confirmed from theory and experiment that the fine nano Bi-2201 stripe phase in Bi-2212 wires is an effective pinning phase of Bi-2212 wires, which can improve the pinning strength of the wires, but the generation mechanism of the fine nano Bi-2201 stripe phase in the wires is still unclear, and the density of the fine nano Bi-2201 stripe phase cannot be controlled. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a preparation method of Bi-2212 precursor powder for significantly improving the density of Bi-2201 nano-stripe phases in Bi-2212 wires. The preparation method sets the components of the precursor liquid, and combines the fine regulation of the heat treatment process, to eliminate the Bi-2201 phase that can be monitored by XRD, and at the same time control the molar ratio of Sr and Ca in the powder within a suitable range, so as to prepare Bi-2212 precursor powder for significantly improving the density of Bi-2201 nano-stripe phases in Bi-2212 wires.

[0005] To achieve the above object, the technical scheme adopted by the present application is: a preparation method of Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wire, characterized in that the method controls the composition of precursor liquid, adjusts by fine heat treatment method, and controls the molar ratio of Sr and Ca within a suitable range to obtain Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wire.

[0006] The preparation method of Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wire described above is characterized in that the method comprises the following steps: Step one, prepare Bi-2212 precursor liquid according to the chemical formula of target Bi-2212, and then prepare Bi-2212 raw powder based on the Bi-2212 precursor liquid; Step two, heat treat the Bi-2212 raw powder prepared in step one to obtain Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wire.

[0007] The preparation method of Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wire described above is characterized in that the chemical formula of target Bi-2212 in step one is Bi 2.12 Sr 1.94 Ca 0.89 Cu 2.0 O x , x represents a non-fixed value.

[0008] The setting of precursor liquid component in the present application is the key to ensure the subsequent powder component within a specific range and is the prerequisite for obtaining Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wire.

[0009] The preparation method of Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in Bi-2212 wire described above is characterized in that the preparation method of Bi-2212 raw powder in step one is spray pyrolysis; the process of spray pyrolysis is: dissolving Bi2O3, SrCO3, CaCO3 and Cu in nitric acid to obtain a nitrate mixed solution, and using a spray pyrolysis equipment to prepare Bi-2212 raw powder.

[0010] The present application uses spray pyrolysis, a common powder preparation method, which has mature preparation technology, relatively common preparation equipment, simple operation and low cost, providing great convenience for the preparation of Bi-2212 raw powder and facilitating the engineering application and popularization of the preparation method of the present application.

[0011] The preparation method of the Bi-2212 precursor powder for significantly increasing the density of Bi-2201 nanostripe phase in Bi-2212 wire, characterized in that the heat treatment process in step two is: in an air environment, the Bi-2212 green powder is subjected to segmented heat preservation and grinding in the interval of 640-850 DEG C, and then is subjected to heat preservation at 865 DEG C ± 10 DEG C for 10 hours and then is ground, to obtain the powder; The second phase in the powder is analyzed by XRD, and ICP analysis is performed when the Bi-2201 phase does not appear in the powder, and when the molar ratio of Sr to Ca in the powder is 2.33 and the variation coefficient is not more than 1%, and the relative error of the molar number of each element in the powder to the molar number of each element in the target Bi-2212 in step one is less than 7%, the heat treatment is completed, and the Bi-2212 precursor powder for significantly increasing the density of Bi-2201 nanostripe phase in Bi-2212 wire is obtained.

[0012] Since the fine nanometer Bi-2201 stripe phase in the Bi-2212 wire is an effective pinning phase of the Bi-2212 wire, it can improve the pinning strength of the wire; but if the Bi-2201 phase can be monitored by XRD in the powder, on the one hand, it means that the Bi-2201 phase in the powder is too much, and on the other hand, it indirectly reflects that the size of the second phase is large, the content of the ineffective pinning phase is increased, and finally the pinning effect of the fine nanometer Bi-2201 phase is weakened. The present application controls the Bi-2212 precursor liquid to be a specific component, and combines the fine adjustment of the heat treatment process to remove the Bi-2201 phase that can be monitored by XRD in the powder, while ensuring that the molar ratio of Sr to Ca is in a suitable range, to prepare the Bi-2212 precursor powder for significantly increasing the density of Bi-2201 nanostripe phase in Bi-2212 wire, so that the fine stripe-shaped nanometer Bi-2201 pinning phase with higher density than the conventional wire exists in the prepared Bi-2212 wire, which is beneficial to improve the pinning strength of the Bi-2212 wire and beneficial to the maintenance of the current-carrying performance of the wire at low temperature and high field, and lays a foundation for the application of the wire in low-temperature high-field magnets.

[0013] The application can ensure the stability of the Bi-2201 nanostripe phase density in the final wire, significantly improve the Bi-2201 nanostripe phase density, and finally improve the pinning performance of the Bi-2212 wire, ensure the excellent current-carrying performance of the wire at low temperature and high field, and promote the engineering application of the wire by fine adjustment of the heat treatment process, combination of XRD data analysis, and combination of ICP analysis of the molar ratio of Sr and Ca in the powder after heat treatment in a suitable range.

[0014] The preparation method of the Bi-2212 precursor powder for significantly improving the Bi-2201 nanostripe phase density in the Bi-2212 wire, the temperature of the segmented heat preservation is 640 DEG C, 800 DEG C, 820 DEG C, 850 DEG C in turn.

[0015] Compared with the prior art, the application has the following advantages: 1. The application adopts specific Bi-2212 precursor liquid components, determines the fine heat treatment process of the powder, and combines simple and rapid powder phase and component characterization methods to first determine a Bi-2212 precursor powder component and its preparation method for significantly improving the Bi-2201 nanostripe phase density in the Bi-2212 wire, and finally improves the pinning performance of the Bi-2212 wire.

[0016] 2. The preparation method of the application is simple, low in cost, strong in controllability and operability, and high in output-input ratio, which is conducive to the rapid application in Bi-2212 superconducting materials and further promotes the engineering application of Bi-2212 superconducting materials in high-field magnets.

[0017] 3. The Bi-2212 wire prepared in the application has a Bi-2201 nanostripe phase density improved by more than 57% compared with the conventional Bi-2212 wire.

[0018] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The TEM image of the Bi-2212 wire prepared in Example 1 of the application.

[0020] Figure 2 The TEM image of the Bi-2212 wire prepared in Comparative Example 1 of the application. DETAILED DESCRIPTION

[0021] Example 1 The method of this example includes the following steps: Step one, according to the chemical formula Bi 2.12 Sr 1.94 Ca 0.89 Cu 2.0 O x Bi2O3, SrCO3, CaCO3 and Cu are dissolved in nitric acid to obtain a mixed nitrate solution, and a Bi-2212 raw powder is prepared by using a spray pyrolysis device; Step two, the Bi-2212 raw powder prepared in step one is sequentially subjected to segmental heat preservation at 640℃, 800℃, 820℃ and 850℃ and then ground, and then subjected to heat preservation at 865℃±10℃ for 10h and then ground to obtain a powder; the second phase in the powder is analyzed by XRD, and no Bi-2201 phase appears in the powder, and then ICP analysis is performed, the molar ratio of Sr to Ca in the powder is 2.33, the variation coefficient of the molar ratio of Sr to Ca is 0.91%, and the maximum relative error of the molar number of each element in the powder to the molar number of each element in the target Bi-2212 is 6.7%, and the heat treatment is completed to obtain a Bi-2212 precursor powder which significantly improves the density of Bi-2201 nanostripe phase in Bi-2212 wire.

[0022] The Bi-2212 precursor powder which significantly improves the density of Bi-2201 nanostripe phase in Bi-2212 wire obtained in this example is assembled into a tube, and combined with a bundled drawing process to obtain a Bi-2212 wire, and the Bi-2212 wire is subjected to microscopic analysis, as shown in FIG. 1, the Bi-2212 wire has 35 nanometer Bi-2201 stripe phases. Figure 1

[0023] Comparative Example 1 The method of this example includes the following steps: Step one, according to the chemical formula Bi 2.07 Sr 1.94 Ca 0.89 Cu 2.0 O x Bi2O3, SrCO3, CaCO3 and Cu are dissolved in nitric acid to obtain a mixed nitrate solution, and a Bi-2212 raw powder is prepared by using a spray pyrolysis device; ​Step two, under the air environment, the Bi-2212 raw powder prepared in step one is sequentially kept at 640 DEG C, 800 DEG C, 820 DEG C, 850 DEG C and grinded, then kept at 865 DEG C ± 10 DEG C for 10 hours and grinded, the second phase in the powder is analyzed by XRD, no Bi-2201 phase appears in the powder, then ICP analysis is carried out, the molar ratio of Sr and Ca in the powder is 2.22, the variation coefficient of the molar ratio of Sr and Ca is 1.3%, and the maximum relative error of the molar number of each element in the powder and the molar number of each element in the target Bi-2212 is 2.2%, the heat treatment is completed, and the Bi-2212 precursor powder is obtained.

[0024] The Bi-2212 precursor powder obtained in the present example is assembled into a tube, combined with the bundle drawing process, and the Bi-2212 wire is obtained. Figure 2 As shown in the microstructure analysis of the Bi-2212 wire, the Bi-2212 wire has 22 nanometer Bi-2201 stripe phases, and the density of the nanometer Bi-2201 stripe phase of the Bi-2212 wire obtained in example 1 is 1.59 times that of the Bi-2201 nanometer stripe phase in the present example.

[0025] The current-carrying performance of the Bi-2212 wire obtained in example 1 and the present example is tested at 4.2K self-field and 12T, and the current-carrying performance of the Bi-2212 wire in example 1 is only attenuated by 58%, while the current-carrying performance of the Bi-2212 wire in the present example is attenuated by 65%.

[0026] The above is only the preferred embodiment of the present application, and does not limit the present application, any simple modification, change and equivalent structure change according to the technical essence of the present application to the above embodiment are still within the protection scope of the technical solution of the present application.

Claims

1. A method for preparing Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire, characterized in that, This method controls the composition of the precursor liquid, adjusts it with a fine heat treatment method, and controls the molar ratio of Sr to Ca within a suitable range to obtain Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire.

2. The method for preparing Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire according to claim 1, characterized in that, The method includes the following steps: Step 1: Prepare Bi-2212 precursor solution according to the chemical formula of the target Bi-2212, and then prepare Bi-2212 raw powder based on the Bi-2212 precursor solution; Step 2: Heat-treat the Bi-2212 raw powder prepared in Step 1 to obtain Bi-2212 precursor powder that significantly improves the phase density of Bi-2201 nanostripes in Bi-2212 wire.

3. The method for preparing Bi-2212 precursor powder with significantly improved Bi-2201 nanofiber phase density in Bi-2212 wire according to claim 2, characterized in that, The chemical formula of the target Bi-2212 mentioned in step one is Bi. 2.12 Sr 1.94 Ca 0.89 Cu 2.0 O x , where x represents a non-fixed value.

4. The method for preparing Bi-2212 precursor powder with significantly improved Bi-2201 nanofiber phase density in Bi-2212 wire according to claim 2, characterized in that, The preparation method of Bi-2212 raw powder in step one is spray pyrolysis; the spray pyrolysis process is as follows: Bi2O3, SrCO3, CaCO3 and Cu are dissolved in nitric acid to obtain a nitrate mixed solution, and Bi-2212 raw powder is prepared by spray pyrolysis equipment.

5. The method for preparing Bi-2212 precursor powder with significantly improved Bi-2201 nanofiber phase density in Bi-2212 wire according to claim 2, characterized in that, The heat treatment process described in step two is as follows: Bi-2212 raw powder is kept at 640℃~850℃ in sections and ground in an air environment, and then kept at 865℃±10℃ for 10 hours and ground to obtain powder. XRD analysis was used to analyze the second phase in the powder. When no Bi-2201 phase appeared in the powder, ICP analysis was performed. When the molar ratio of Sr to Ca in the powder was 2.33 and the coefficient of variation did not exceed 1%, and the relative error between the molar number of each element in the powder and the molar number of each element in the target Bi-2212 in step one was less than 7%, the heat treatment was completed, and Bi-2212 precursor powder with significantly improved Bi-2201 nano-stripe phase density in Bi-2212 wire was obtained.

6. The method for preparing Bi-2212 precursor powder with significantly improved Bi-2201 nanofiber phase density in Bi-2212 wire according to claim 5, characterized in that, The segmented insulation temperatures are 640℃, 800℃, 820℃, and 850℃, respectively.

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